Though there's no formula for great creative writing, there are some strategies you can use that will make sure you're able to cross the two biggest hurdles on the day: finding something to write about and writing about it in a way that actually engages your reader.
Examples from online...
There's LOADS of creative writing available online, and it's always a good idea to see what other people are doing and magpie ideas from them.
And remember what the great 20th Century artist Picasso once said: "Good artists copy, great artists steal!"